It honestly doesn’t matter which order you create them in – the important thing is that measures always operate within context. For example suppose we have the following date harvest measure:
Harvest Max Date =
MAX( Dates[Date] ),
ALLSELECTED( Dates )
On this page, with only one slicer it returns December 31, 2021.
However, on a different page with multiple slicers, and thus different context, it evaluates to June 30, 2020 even though the measure remains completely unchanged, as does the date slider.
Now by changing the context back, either by manipulating the interaction between visuals via “edit interactions”, or by changing the filter context of the measure or both, we can control which context the measure evaluates and which it ignores. Make sense? Absolutely fundamental concept to understanding and properly applying DAX.
I would definitely recommend going back through @sam.mckay’s Mastering DAX Calculations course. I personally have been through this course four separate times at different points in my training and have picked up new understanding each time through it.
I hope this is helpful.